1. Field of the Invention
The present invention relates to a colorimetric value calculating method, a profile generating method, a color conversion method, a color conversion apparatus, and a computer-readable recording medium having a color conversion program recorded therein, in which, in an observational environment where both transmissive and reflective light sources coexist, colorimetric values of a print made up of an image formed on a light-transmissive medium are calculated.
2. Description of the Related Art
With significant advances in inkjet technology in recent years, it has been become possible for inkjet printers to produce large color prints of high quality at high speeds. Inkjet printers are not only popular for private or home use, but also are widely used in commercial applications nowadays. Inkjet printers enable prints to be made on POP (Point Of Purchase) posters, wall posters, large-size mediums such as outdoor advertisements and billboards, roll mediums, and thick hard mediums.
There are a wide variety of print mediums (hereinafter also referred to as “mediums”) available for use in prints in order to meet various commercial demands. For example, such print mediums include paper mediums including synthetic paper, thick paper, aluminum-evaporated paper, etc., resin mediums made of vinyl chloride, PET, etc., and tarpaulin paper made of a woven fiber cloth with synthetic resin films applied to both surfaces thereof.
Since advertisement prints are expected to be effective in arousing consumers' motivation to buy advertised products through visual sensation, the finish of colors of the prints (printed mediums) is of particular importance. Heretofore, there have been disclosed various color matching technologies, such as a method of generating an ICC (International Color Consortium) profile, a method of adjusting a designated color, etc., as print color managing means.
Advertisement prints are displayed in a variety of places including outdoor areas, indoor areas, and spotlighted exhibition sites. Generally, the spectral characteristics (spectral energy distribution) of environmental light as an observational light source for prints vary depending on different places where the prints are displayed. As a result, in cases where the observational light sources differ, even though the same print is viewed, the spectral characteristics of light that ultimately reaches the retinal wall of eyes of the observer are different, and therefore, the appearance of the print (impression of colors) to the observer is subject to variation, although the tendency may differ from observer to observer. As a consequence, if the observational environment in which a print is produced (i.e., the location where the printer is installed) and the observational environment in which the print is displayed differ greatly from each other, then the print may possibly fail to exhibit desired colors.
As one method for solving such problems, Japanese Laid-Open Patent Publication No. 2007-081586 discloses a method and apparatus for storing independently spectral data of a print, and a plurality of light source spectral data. A profile appropriate for an observational light source is generated each time that the observational light source is set up. This publication states that the method and apparatus can generate profiles corresponding to respective different observational light sources for colorimetric measurement in a reduced number of man-hours, and can perform appropriate color management for prints depending on such observational light sources.
Further, in Japanese Laid-Open Patent Publication No. 2003-298854, as spectral data which is used when a profile is generated, in place of the spectral reflectance of the print, it is disclosed that the spectral transmittance of a film or the like can be used. (Refer to paragraph [0070] in the specification of Japanese Laid-Open Patent Publication No. 2003-298854.)
However, with a print consisting of an image formed on a light-transmissive medium, in the case of an observational environment in which both transmissive and reflective light sources coexist, or stated otherwise, in the event the print is displayed under the influence of both a transmissive light source and a reflective light source, problems occur in that colors of the print cannot be managed appropriately.
Moreover, the method and apparatus disclosed in Japanese Laid-Open Patent Publication No. 2007-081586 and Japanese Laid-Open Patent Publication No. 2003-298854 provide no consideration for a situation where an observational environment is provided in which both transmissive and reflective light sources coexist.